I've done something similar, though not in that exact position. The humiliation is worth it. Love licking my wife's clit while she's getting fucked, knowing that I'm amplifying the pleasure she's getting from another man's cock. Love licking his shaft as it slides in and out of her, tasting her juices on him. And love licking his balls, knowing that the stimulation I'm providing will both increase his enjoyment as he uses my wife's body and cause those balls to shoot a bigger load of extramarital cum deep into the woman I love.
A good bull will use the husband too. The bull has every right to do this and make the cuck clean off his cock too. The bull should insure that the cuck eats all of the sperm out of the wife and that the wife gets another orgasm from that. This way the bull will eventually own the couple as his sex slaves. Good for the bull and good for the couple